1. Field of the Invention
Embodiments of this invention relate generally to disk drives of the type generally used for storing digital data, and in particular to methods and devices for applying a temperature-compensated write current to read/write heads during disk drive write operations, and disk drive systems incorporating the same.
2. Description of Related Art
Modern computers require media in which digital data can be quickly stored and retrieved. Magnetizable (hard) layers on disks have proven to be a reliable media for fast and accurate data storage and retrieval. Disk drives that read data from and write data to hard disks have thus become popular components of computer systems.
FIG. 1 illustrates a conventional disk drive write system 2 comprising a disk drive microprocessor 4, control logic 6, read/write preamplifier 8, coil 10, read/write core 12, and hard disk 14. The read/write preamplifier 8 further includes a write current source 16. During write operations, a computer 18 communicates through controller 20 with the disk drive microprocessor 4. In response to commands from the controller 20, the disk drive microprocessor 4, by means of control logic 6, provides a write signal 34 to the read/write preamplifier 8. The read/write preamplifier 8 energizes the write current source 16, which applies a write current 22 through coil 10, inducing magnetic flux 24 to form within the read/write core 12 and fringe across a core gap 26. The strength of the fringing magnetic flux 24 varies directly with the amount of write current 22 flowing through the coil 10. The fringing magnetic flux 24 passes through magnetizable material 28 within the hard disk 14 located beneath the core gap 26, causing that material to become magnetized and oriented in the direction of the magnetic flux 24. As the hard disk 14 spins and the read/write core 12 passes over other magnetizable material during the course of a write operation, the direction of the write current 22 may be reversed, causing the fringing magnetic flux 24 to be oppositely oriented and reversing the polarity of the magnetizable material 28. As the fringing magnetic flux 24 goes through a series of such reversals, a data pattern is formed within the hard disk 14 from the polarity sequence of the magnetizable material 28.
In disk drive systems, the magnetizable material within the disk is "hard," meaning that once the magnetizable material has been polarized and a data pattern established as described above, the polarity of the magnetized material and hence the data pattern will remain intact until a magnetic flux of sufficient magnitude reverses the polarity and changes the pattern. The measure of a magnetized material's hardness or ability to resist magnetic change is coercivity, H.sub.c, and a magnetized material's coercivity once a magnetizing flux has been removed is known as its residual or remnant coercivity, H.sub.cr. Another property of importance to consider is a magnetized material's intensity of magnetization, M, and its residual or remnant intensity of magnetization once a magnetizing flux has been removed, M.sub.r. Higher values of H.sub.cr and M.sub.r mean that a higher reverse-polarity magnetic flux is required to reverse the polarity of the magnetized material.